基于化学组分的铁观音茶梗和叶茶模式识别研究

Chemicals in Stems and Leaves of Tieguanyin Tea

铁观音茶梗与其叶茶(毛茶和净茶)的化学组分存在一定差异,为全面揭示茶梗的化学组成,以便进一步提高其利用价值,试验比较了3类样品中茶多酚(TPs)、黄酮类(Fs)、水浸出物(WE)、游离氨基酸总量(FAAs)与组分、可溶性糖(WSS)以及儿茶素类、生物碱等物质含量差异,并采用二维“点集”分布和主成分分析(PCA)对其主要成分进行化学模式识别研究。结果表明,净茶中TPs、Fs、没食子儿茶素(GC)、表儿茶素(EC)和可可碱(TB)含量约是茶梗的2倍,WE、FAAs、WSS含量比茶梗高10%~30%,表没食子儿茶素没食子酸酯(EGCG)、表儿茶素没食子酸酯(ECG)、表没食子儿茶素(EGC)和咖啡碱(CAF)含量比茶梗高3~4倍;5种氨基酸组分在茶梗样中较低,6种有机酸在3类样品中含量差异不明显。二维“点集”分布图表明,茶梗与净茶中差异较大的组分依次是TPs、Fs、WE。基于儿茶素和生物碱的PCA表明,茶梗投影圈距离净茶和毛茶投影圈质心均较远,显示出很好的类群区分;基于氨基酸组分的PCA表明,前2个主成分累积方差贡献度为88.47%,茶梗与净茶和毛茶基本分离,区分度较好;有机酸组分对3个群体的分离度较差。以上结果可为提高茶梗综合利用价值提供参考。

Chemical compositions of Tieguanyin tea varied in the stems and leaves.And,the“raw material”was product of primary processing and contained stems and leaves,whereas,the“net tea”picked out from the“raw tea”was basically stem-free.Selected chemical constituents including polyphenols(TPs),flavonoids(Fs),water extract(WE),free amino acids(FAAs),water soluble sugars(WSS),catechins and alkaloids in the stems,leaves and raw material from the tea bushes were analyzed and compared aiming for marketing improvement.Three samples of Tieguanyin tea were used in the study to characterize the compositional differences by means of two-dimensional scatter plots(2DSP)and principal component analysis(PCA).It was found that the leaves had twice as much TPs,Fs,TB,GC and EC as the stems;WE,FAAs and WSS,10%to 30%higher;and,CAF,EGCG,ECG and EGC,3 to 4 times higher.The stems had a slightly lower amino acid content than the sorted leaves but similar on organic acids.The 2DSP revealed that the TPs,Fs and WE in stems and leaves significantly differed.The PCA based on catechins and alkaloids showed that the distribution pattern of the chemicals in the stems sat significantly apart from that of the raw material or the sorted leaves on the plot.The amino acid-based PCA also exhibited significant differences between the stems and the leaves.The two top-ranking principal components of the chemical constituents constituted 88.47%of the total variance among them.Whereas,the organic acids did not appear to be a viable candidate for differentiating the 3 samples of Tieguanyin tea.The results also provided information for the utilization of tea stems.